Ballistics

What is Forensic Ballistics Ballistics: The Science of the mechanics that deals with motion, behavior, and effects of projectiles Forensic Ballistics: Science of analyzing firearm and weapon usage in crimes Firearm Identification Firearm components Ammunition/Ammunition components Toolmark analysis

What are Projectiles? Projectiles: An object propelled through space an exertion of force that ceases after launch Bullets, gravity bombs, rockets, scrape metal

Kurt Cobain (2/20/67 – 4/5/94)

What is a Ballistic Body? Ballistic Bodies are those that are free to move, behave, and be altered or modified in appearance and contour by ambient conditions, substances, and forces. Ambient = surrounding Contour = path Example: Pitching a baseball

Ballistic History 9th century A.D. - Chinese discover gun powder Potassium Nitrate (KNO3), charcoal, sulfur Expands to 6 times its size when heated Fireworks and cannonballs 14th century A.D. – Europe Matchlock guns Contained a barrel and wick on a piece of wood 18th century A.D. – Europe Cartridges: case that holds a bullet, primer powder, and gun powder Bullet: pointy projectile that is released when a firearm is discharged

Samuel L. Colt 1835: Colt creates the first firearm that can be shot multiple times without reloading

Ballistic History In Court 1902: 1st court case involving firearms evidence Oliver Wendell Holmes proved murder weapon by test shooting

Alphonse Gabriel Capone a. k. a. “Scarface” & the St Alphonse Gabriel Capone a.k.a.“Scarface” & the St. Valentines Day Massacre

Ballistic History cont… Calvin Goddard Pioneer for Firearms Identification Acquired data from all well-known gun manufacturers Established database Comparison Microscopes to compare and contrast test fires Coined term “Forensic Ballistics” Established the Bureau of Forensic Ballistics in NYC 1929: St Valentines Day Massacre Event led to the opening of ballistic crime detection laboratory

Ballistic History cont… 1930: Earliest gunshot residue (GSR) test is performed  It is principally composed of burnt and unburnt particles from the explosive powder – and possibly the components of the bullet, cartridge case, and firearm 1968: 1st use of scanning microscope for comparing GSR.

History cont… 1992: FBI established Drugfire database Compiles details on bullet and cartridge markings 1996: U.S. Bureau of Alcohol, Firearms, and Tobacco (AFT) establish database for spent ammunition 2000: FBI and AFT begin merging databases

Types of Guns 1. Long guns Shot guns and rifles Rifles  bullets Shot guns  Small round pellets (shot) or a single projectile (slug) Require 2 hands for accurate firing

Types of Guns 2. Handguns One hand to operate Pistols  single bullet Revolvers Cylinder that holds the cartridges turns as gun is fired, allows for several cartridges to be fired in rapid succession Holds 6 cartridges

Automatic Weapons Semiautomatic Holds up to 10 cartridges into a magazine (clip) 1 bullet fired per pull of the trigger

Automatic Weapons Fully Automatic Multiple rounds are fired when the trigger is held down

Anatomy of a Cartridge Bullet: Projectile that is extracted from the cartridge Usually lead or copper Metal-jacketed, hollow-pointed, or plastic

Anatomy of a Cartridge cont… Primer powder Struck by firing pin Pressure causes ignition Flash hole Delivers the explosive charge from primer powder to gun powder

Anatomy of a Cartridge cont… Headstamp Bottom of the cartridge casing Caliber and Manufacturer info

Gun Ballistics From the time of shooting to the impact upon a target Broken down into 4 different branches Internal Ballistics Transition Ballistics External Ballistics Terminal Ballistics

Internal Ballistics Def: The study of the processes that originally accelerate the bullet Example: The passage of a bullet through the barrel of a rifle

Rifling (Internal Ballistics) Rifling are helical (spiral) grooves that are cut into a bore of a firearm Bore: Interior of a firearm Lands: Raised portion of rifling. Grooves: Indented portion of rifling Caliber: Diameter of the bore Usually expressed hundredths of an inch or mm

Why Significant? (Rifling) No 2 rifled barrels are the same Even those manufactured by the same company Lands and Grooves leave marks on the bullet As unique as fingerprints Wear and tear from machine makes each gun unique

Why Significant cont… Increase Accuracy Increase Speed Lands and grooves cause bullet to spin Increase Speed The faster a bullet spins the easier it cuts through the air, thus allowing it to travel faster

Transition Ballistics Def: Study of the projectiles behavior once it leaves the barrel and the pressure behind the projectile is equalized This accounts for the loud sound a gun makes when fired

External Ballistics Def: Study of the projectile through air and space There are two main forces that act upon the projectile Gravity: drops the bullet Air resistance: decelerates the bullet

Bullet Movement (Ext. Ballistics) Bullet Drop 3 feet over a distance of 500 yards Bullet Rise Bullet rises before it drops Due to force from being fired Rise can be up to about 14 inches

Bullet Drop and Bullet Rise

JFK Autopsy Pictures

Factors that would affect Bullet Movements Gun Type Bullet Weight Weather conditions How about for extremely long ranges (missiles)? Coriolis Effect Deflection of an object due to the rotation of the Earth

Terminal Ballistics Def: Study of the interaction of the projectile with its target Also referred to the stopping power when dealing with human or living tissue Only relevant for smaller projectiles

3 Classes of Bullets Terminal Ballistics depends on the class of bullet Maximum Accuracy Maximum Damage w/Total Penetration Maximum Damage w/Controlled Penetration

Total Penetration Bullets Want to focus the most momentum on the smallest possible target Armored targets/Large game animals Tips are… Sharp Lead covered in metal coat Resist Deformation

Controlled Penetration Bullets Designed to inflict maximum damage on a living target Designed to increase surface area upon impact Expanding Bullets (Hollow Tip) Sharp tips with nothing behind them Covering opens up upon impact Larger Hole Slows Impact “Mushroom” effect

2. Fragmenting Bullets 3. Frangible Bullets Designed to break apart upon impact Differ from that of hollow points in that they do NOT stay in one piece Used for small game 3. Frangible Bullets Similar to Fragmenting…break apart upon impact Differ: NOT hollow Hostage Situations

Gun Shot Residue (GSR) GSR = residues of smoke and particles of unburned powder carried sideways from the firearm by the expansion of gases as the bullet is fired. Stick to shooter

Gun Shot Residue Residue can travel out of the gun from distances of 3-5 feet Sticks to both shooter and victim Amount of GSR decreases as the distance between firearm and victim increases Helps to determine distance between shooter and victim